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Re: Extinction once again (was Re: ARE ORNITHOPODS BORING?)
On Sat, 17 Feb 2001, David Marjanovic wrote:
> 1. This regression took _4 million years_, spanning quite some time before
> and after the K/T.
...adding stress to species which nested on the shores of the "Oceans of
Kansas." Habitat loss is the main cause of today's extinctions--why
would we doubt that it was important in other times--especially when we
know that vast tracts of potential nesting territory were reduced to zero?
> 2. Due to some odd effects of earth axis precession or so (I can
dig up the
> ref later), sea level dropped in the western half of the northern and the
> eastern half of the southern hemisphere whereas it rose in the rest of the
> world. Yet the extinction was global.
Lest we take news reports too literally, we should remind ourselves that
extinction is only recorded in one location!
> 3. You are not trying to suggest that ALL Maastrichtian non-_neornithean_
> dinosaurs nested in "wetlands"!?!
> 4. Lots of terrestrial egg-laying vertebrates survived (turtles, crocs,
> lizards/snakes, tuataras, monotremes...)...
They are mostly very small and can hide their nests in a greater variety
of places. Crocs are totally dependent on wetlands, though.
> 5. Marsupials, for example, were severely hit. How come?
Their extinctions are timed to placental radiation at the K/T. So
replacement is a thoroughly respectable hypothesis for this. Why wouldn't
diverse creatures have diverse reasons for their disappearance--unless
we're trying to shoe-horn observable phenomena into non-observable
> 6. Plankton (and all animals with planktonic larvae) was severely hit, which
> is not easy to explain with a regression.
Not yet timed to terrestrial extinctions.